1. Field of the Invention
The present invention relates to an apparatus for supporting a power train in a vehicle's engine room. More particularly, the present invention pertains to a power train supporting apparatus that supports the power train so as to suppress the deformation of a partition separating a vehicle's engine room from a passenger compartment during a head-on collision.
2. Description of the Related Art
Monocoque structures, in which a chassis frame and a body of a vehicle are integral, are widely employed in automobiles. A power train, which includes an engine and a transmission, is accommodated in an engine room. A passenger compartment is located at the rear of the engine room. The engine room is defined between a pair of side members, a front cross member, which connects the front ends of the side members, and a toe board, which connects the rear ends of the side members. The toe board separates the engine room from the passenger compartment.
The energy of a head-on collision causes a rearward contraction of the engine room (including the side members). The energy produced during the collision deforms the side members, among other things, and is thus absorbed by the deformation of these parts. Accordingly, the energy that is transmitted to the power train is reduced. This suppreses the rearward displacement of the power train and prevents contact with the toe board. As a result, the deformation of the board is prevented. To efficiently absorb the impact of the collision in this manner, research related with the cross-sectional shape of the side members and other associated members has been conducted.
There are cases in which it is desirable for an automobile's hood to be located at a relatively low position. Therefore, there are types of automobiles having a power train, the upper part of which is inclined toward the passenger compartment. This structure brings the upper part of the power train closer to the toe board. As a result, the power train is more apt to contact the toe board during head-on collisions than in structures in which the power train is oriented in an upright or vertical manner. Such contact can cause deformation of the toe board.
Japanese Unexamined Patent Publication No. 5-338445 describes an apparatus to cope with the above problem. As shown in FIG. 6, a supporting apparatus 100 includes side members (not shown), one of which is located on each side of a power plant (power train) 102, a front cross member 104 connecting the front ends of the side members, a front center member 103 supporting the power train 102, and a toe board 107 defining an engine room 106 and a passenger's room 101.
The center member 103 has a first holder 108 located near its front end and a second holder 109 located near its rear end. The power train 102 has first and second brackets 110, 111 located at positions corresponding to the first and second holders 108, 109, respectively. The first bracket 110 is rotatably connected to the first holder 108 by a bolt 112. The second bracket 111 includes a guide hole 113 extending diagonally upward toward the right, as viewed in the drawing. A bolt 114 is inserted into the hole 113 to connect the second bracket 111 to the second holder 109. The hole 113 enables the second bracket 111 to move with respect to the second holder 109.
When the automobile collides head-on, the energy of the collision applied from the front (the left in FIG. 6) crushes the side members and the center member 103, axially. The first holder 108 and the first bracket 110 enable the power train 102 to be rotated while also pushing the lower portion of the power train 102 toward the rear. This causes the power train 102 to be displaced in an upwardly inclined direction. The movement of the power train 102 is guided by the hole 113. In this manner, the entire power train 102 is rotated about its center of gravity in a counterclockwise direction, as viewed in the drawing. Consequently, the power train 102 is positioned upright with its upper section separated from the toe board 107.
This structure reduces the likelihood that the power train 102 will contact the board 107 during head-on collisions despite the upper section of the power train being inclined toward the passenger compartment 101. Accordingly, the apparatus 100 reduces the likelihood that the power train 102 will damage the toe board 107.
However, while the apparatus 100 enables the power train 102 to be positioned upright, excessive colliding energy increases the rearward movement of the power train 102. This may cause the power train 102 to contact and deform the toe board 107.
As when using a supporting apparatus that holds a power plant upright, the timing of when the power train 102 contacts the toe board 107 is determined by the length of the side members and the center members 103. Thus, the deformation of the toe board 107 that is caused by the power train 102 is affected by the length of the section between the nose of the automobile and the toe board 107, or the crush zone. The length of deformation in the colliding direction, or the crush stroke, is long in automobiles having a long crush zone. Accordingly, the toe board is more likely to be deformed in automobiles having a short crush zone during collisions than in automobiles having a long crush zone.
Smaller automobiles are advantageous from the viewpoint of energy consumption and environmental problems. Thus, the number of compact automobiles has increased during recent years. Accordingly, it is desirable that compact automobiles have the same energy absorbing performance as large-size automobiles. However, the employment of the prior art power train supporting apparatus in compact-size and middle-size automobiles results in an impact absorbing capability that is lower than that of large-size automobiles.